PARIS -- The planet's temperature is rising, sea levels threaten to swallow coastlines and the world's residents want to know, more than ever, how worried to be. An authoritative answer comes this week.

Some 500 scientists and officials convened in Paris on Monday for a week of word-by-word editing of a long-awaited report on how fast the world is warming, how serious it is -- and how much is the fault of humans.

The report by the Intergovernmental Panel on Climate Change, to be released Friday, could influence what many governments and businesses do to fight global warming. It will be watched closely in the United States, whose government stands accused by many around the world of underplaying the peril.

Scientists are keeping quiet about the report's contents, but say it is both more specific and more sweeping than previous efforts to chart hotter summers, snowless ski seasons and breakaway ice sheets and what they mean for the Earth's future.

"At no time in the past has there been a greater global appetite" for reliable information on global warming, the panel's chairman, Indian climatologist Rajendra Pachauri, told the conference.

The report is expected to give a grim warning of continued temperature rises between now and 2100 and reiterate that people-created pollution is partly to blame. But debate may arise at this week's closed-door meetings over how much sea levels are rising.

Early drafts of the new document foresee smaller sea level rises than the last report, in 2001. But many top scientists reject the new figures, saying they are not new enough: They do not include the recent melt-off of big ice sheets in two crucial locations -- Greenland and Antarctica.

Many fear this melt-off will mean the world's coastlines are swamped much earlier than previously thought. Others believe the ice melt is temporary and won't play such a dramatic role.

In the past, the panel did not expect a large melt of ice in west Antarctica and Greenland this century. Their forecasts were based only on how much the sea level would rise because of melting glaciers, which are different from ice sheets, and the physical expansion of water as it warms.

In Paris this week, science and politics converge as climate experts work with diplomats to finalize the wording of the IPCC's report, the first of four major global warming documents by the panel this year.

"We're hoping that it will convince people that climate change is real and that we have a responsibility for much of it, and that we really do have to make changes in how we live," said Kenneth Denman, one of the report's authors.

The panel, created by the United Nations in 1988, releases its assessments every five or six years -- although scientists have been observing climate change since as far back as the 1960s.

While critics call the panel overly alarmist, it is by nature cautious because it relies on input from hundreds of scientists, including skeptics and industry researchers. And its reports must be unanimous, approved by 154 governments -- including the United States and oil-rich countries such as Saudi Arabia.

Pachauri said the report would make "significant advances" over the 2001 report, addressing gaps in that document, reducing uncertainties and adding new knowledge about past changes in climate.

As the panel meets, the planet is the warmest it has been in thousands of years -- if not more -- and awareness of the consequences of climate change is growing.

Last week, U.S. President George W. Bush referred to global warming as an established fact, after years of arguing that not enough was known about global warming to do anything about it.

Indonesia's environment minister warned on Monday that rising sea levels stand to inundate some 2,000 of his country's more than 18,000 islands by 2030.

And new data released Monday by the U.N. Environment Program showed that 30 reference glaciers lost about 66 centimeters (2.2 feet) in thickness on average in 2005, for a total loss of 10.5 meters (34.6 feet) on average since 1980.

This week's meetings do not address how to tackle global warming, the subject of a report later this year by the IPCC.

But activists want to ensure that consumers and governments don't sit and wait for the world to get warmer.

Just a few hundred meters (yards) from the conference at UNESCO headquarters, Greenpeace activists strung a banner across the Eiffel Tower to urge swifter action against global warming, reading "It's Not Too Late."